// Copyright (c) 2024 - 2025 IBM Corp.
// All rights reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package option

import (
	"github.com/IBM/fp-go/v2/internal/monad"
)

type optionMonad[A, B any] struct{}

func (o *optionMonad[A, B]) Of(a A) Option[A] {
	return Of(a)
}

func (o *optionMonad[A, B]) Map(f func(A) B) Operator[A, B] {
	return Map(f)
}

func (o *optionMonad[A, B]) Chain(f Kleisli[A, B]) Operator[A, B] {
	return Chain(f)
}

func (o *optionMonad[A, B]) Ap(fa Option[A]) func(Option[func(A) B]) Option[B] {
	return Ap[B](fa)
}

// Monad implements the monadic operations for Option.
// A monad provides a way to chain computations that may fail, handling the
// None case automatically.
//
// The monad interface includes:
//   - Of: wraps a value in an Option
//   - Map: transforms the contained value
//   - Chain: sequences Option-returning operations
//   - Ap: applies an Option-wrapped function to an Option-wrapped value
//
// Example:
//
//	m := Monad[int, string]()
//	result := m.Chain(func(x int) Option[string] {
//	    if x > 0 { return Some(fmt.Sprintf("%d", x)) }
//	    return None[string]()
//	})(Some(42)) // Some("42")
func Monad[A, B any]() monad.Monad[A, B, Option[A], Option[B], Option[func(A) B]] {
	return &optionMonad[A, B]{}
}
